Patent EA-001975-B1 (EA)
Title: Method and apparatus for hydroforming an angled tubular part without inhibiting wrinkles formation
Inventor: NORTON FRANK A
IPC: B21D26/043
Filed: 1998-10-07
Abstract: 1. A method of hydroforming an angled tubular part having portions with first and second axes disposed at an angle of at least 30 degree , comprising: disposing an angled metal tubular black (70) within a generally correspondingly angled die cavity, said tubular blank (70) having an exterior surface, wherein at an angled portion of said tubular blank, said exterior surface has a concave surface portion and a convex surface portion an generally opposite sides of said tubular blank; sealing opposite ends of the tubular blank; providing high pressure fluid to an interior of said tubular blank; expanding said blank late conformity with surfaces defining said die cavity as a result of said providing; applying force to at least one end of the tubular blank (70) so as to create longitudinal flow of metal material within said tubular blank to maintain a wall thickness of said blank within a predetermined range, characterized by: a greater amount of force being applied to a portion of the tubular blank (70) which is longitudinally aligned with said convex surface portion (76) of the tubular blank in comparison with the amount of farce applied for a portion of the tubular blank which is longitudinally aligned with said concave surface portion (75) of the tubular blank so as to create a greater amount of flow of metal material. Toward portions of the tubular blank adjacent said convex surface portion (76) in comparison with portions of the tubular blank adjacent said concave surface portion (75), so as to inhibit wrinkle formation at the portions of the tubular blank adjacent said concave surface portion. 2. The method of claim 1, wherein said forcing is accomplished by applying force to both ends of the tubular blank (70). 3. The method of claim 2, wherein said greater amount of force applied to the portion of the tubular blank which is longitudinally aligned with the convex surface portion (76) of the tubular blank is applied to arcuate edges of said both ends of the tubular blank. 4. The method of claim 1, wherein said forcing is accomplished by applying force to only one end of the tubular blank (70). 5. The method of claim 4, wherein said greater amount of force applied to the portion of the tubular blank which is longitudinally aligned with the convex surface portion (76) of the tubular blank is applied to an arcuate edge of said one end of the tubular blank (70). 6. A method according to claim 1, wherein prior to said inserting, said method comprises bending a generally straight tube blank so as to provide said tubular blank with its angled configuration. 7. A method according to claim 1, wherein said greater amount of force applied to said portion of the tubular blank which is longitudinally aligned with said convex surface portion (76) of the tubular blank in comparison with the amount of force applied for a portion of the tubular blank which is longitudinally aligned with said concave surface portion (75) of the tubular is accomplished by providing tube-end engaging structure (66) that contacts the portion of said one end of the tubular metal blank which is longitudinally aligned with the convex surface portion (76) of the tubular metal blank and is spaced from the portion of said one end of the tubular metal blank which is longitudinally aligned with the concave surface portion (75) of the tubular metal blank (70). 8. A method according to claim 1, further comprising forming axe indentation (80) in an end portion of said tubular blank at a location thereof which is longitudinally aligned with said concave surface portion so as to inhibit flow of metal material towards said portions of said tubular blank adjacent said concave surface portion. 9. A method according to claim 8 including the step of cutting off the end portion of the tubular blank (70) containing said indentation (80) after removal of the formed blank from the die cavity. 10. A method according to claim 9 wherein an indentation (80) is formed in both end portions at the aforesaid location and both end portions containing such indentations are cut off as aforesaid. 11. A hydroforming die assembly for forming a tubular metal blank into an angled tubular part having portions with first and second axes disposed at an angle of at least 30 degree , comprising: a die structure (12) having die parts, which include die surfaces cooperable to define an angled die cavity into which a bent tubular metal blank (70) is to be placed, said bent tubular metal blank having an exterior surface which includes a concave surface portion (75) and a convex surface portion (76) on opposite sides thereof; first and second ram assemblies (16, 18) having respective first and second associated tube-end engaging structures (66) disposed at opposite ends of said die cavity; said tube-end engaging structures being constructed and arranged to be inserted into said opposite ends of said die cavity; said tubs-end engaging structures having false-end engaging surfaces (67) for engaging opposite ends of the tubular metal blank placed in the die cavity; said tube-end engaging structures further comprising parts constructed and arranged to provide hydroforming fluid to an interior of the tubular metal blank; said ram assemblies further comprising a fluid pressurizing system constructed and arranged to increase pressure of said hydroforming fluid provided to the interior of the tubular metal blank sufficient to expand the tubular metal blank into conformity with the die surfaces defining said die cavity; at least one of said tube-end engaging structures being movable by the associated ram assembly into forced engagement with one end of said opposite ends of the tubular metal blank so as to longitudinally compress the tubular metal blank between said tube-end engaging structures and thereby create longitudinal flow of metal material during expansion of the tubular metal blank in order to maintain a wall thickness of the tubular metal blank within a desired range, characterized by: said at least one movable tube-end engaging structure having said tube-end engaging surface thereof constructed and arranged to apply a greater amount of force to a portion of said one end of the tubular metal blank which is longitudinally aligned with the convex surface portion of the tubular metal blank in comparison with as amount of force applied to a portion of said one end of the tubular metal blank which is longitudinally aligned with the convex surface portion (76) of the blank so as to create a greater amount of longitudinal flow of metal towards the convex surface portion (76) of the tubular metal blank in comparison with the amount of longitudinal flow of moral towards the concave surface portion of the tubular metal blank, and wherein said pressure is increased to greater than 2,000 atmospheres, wherein portions of said tubular metal blank have a diameter thereof expanded by greater than 10% of an original diameter thereof, and wherein said wall thickness of said tubular metal blank at said portions is maintained within 10% its original wall thickness. 12. A hydroforming die assembly in combination with a tubular metal blank, for enabling said die assembly to form said tubular metal blank into as angled tubular part having portions with first and second axes disposed at an angle of at least 30 degree , comprising: a die structure having die parts (12), which include die surfaces cooperable to define as angled c3ie cavity into which a bent tubular metal blank is to be placed, said bent tubular metal blank (70) having an exterior surface which includes a concave surface portion (75) and a convex surface portion (76) on opposite sides thereof; first and second ram assemblies (16, 18) having respective first and second associated tube-end engaging structures disposed at opposite ends of said die cavity; said tube-end engaging structures being constructed and arranged to be inserted into said opposite ends of said die cavity; said tube-end engaging structures having tube-end engaging surfaces for engaging opposite ends of the tubular metal blank placed is the die cavity; said tube-end engaging structures further comprising ports constructed and arranged to provide hydroforming fluid to an interior of the tubular metal blank; said ram assemblies (16, 18) further comprising a fluid pressurizing system constructed and arranged to increase pressure of said hydroforming fluid provided to the interior of the tubular metal blank sufficient to expand the tubular metal blank into conformity with the die surfaces defining said die cavity; at least one of said tube-and engaging structures being movable by the associated ram assembly into forced engagement with one end of said opposite ends of the tubular metal blank so as to longitudinally compress the tubular metal bleak between said tube-end engaging structures and thereby create longitudinal flow of metal material during expansion of the tubular metal blank in order to maintain a wall thickness of the tubular metal blank within a desired range, characterized by; said at least one movable tube-end engaging structure having said tube-end engaging surface thereof constructed and arranged to apply a greater amount of force to a portion of said one end of the tubular metal blank which is longitudinally aligned with the convex surface portion (76) of the tubular metal blank in comparison with an amount of force applied to a portion of said one end of the tubular metal blank which is longitudinally aligned with the convex surface portion (76) of the blank so as to create a greater amount of longitudinal flow of metal towards the convex surface portion of the tabular metal blank in comparison with the amount of longitudinal flow of metal towards the concave surface portion (75) of the tubular metal blank, and wherein said tube-end engaging surface is spaced from the portion of said one end of the tubular metal blank which is longitudinally aligned with the concave surf